They have chosen possible the worst inhaler on the market for this group of people

Dr Paul Diggory, Consultant geriatrician

Influenza can be fatal for old people, often through secondary infections patients contract.

The elderly make up between 80 and 90% of those who die from flu.

Two types of inhalers were used in the study, the Diskhaler which is used in Relenza, and a Turbohaler.

Inhaler tests

The researchers from the Mayday Hospital in Croydon, south London asked 73 patients aged 71 to 99, who had not used an inhaler before to test the two types. Thirty-eight were allocated the Relenza Diskhaler, 35 the Turbohaler.

After being shown how to use the Diskhaler, 50% were unable to prepare the device. The proportion unable to use the drug rose to 65% 24 hours later.

In contrast, only two of the patients using the Turbohaler were unable to use the inhaler, with only one unable to use it after 24 hours.

To use the Diskhaler, patients perform a complex procedure to make sure a new blister of powder is in line with a perforator.

Putting the top back on the product pierces the blister and sends the drug into the chamber from which the drug is delivered.

The Turbohaler requires users simply to take off the top and turn the base clockwise and back until a click indicates the inhaler is ready to use.

'Series illness risk'

Dr Paul Diggory who led the research, said : "Elderly people are at particular risk of serious illness if they contract influenza.

"Our study shows that zanamivir treatment for elderly people with influenza is unlikely to be effective.

He told BBC News Online: "Elderly people have particularly difficulty using inhalers, particularly if they have dementia, if they have got arthritis and if they have poor eyesight.

"They have chosen possible the worst inhaler on the market for this group of people."

He said whatever device was used had to be able to deliver a significant amount of the drug deep into the lungs. "If you don't, you could have the best drug in the world, but it would be bog-all good."

Dr Diggory said more research was needed both to find an inhaler the elderly can use, and examine the effect of Relenza on mortality rates in the elderly.

Flu 'cure'

When Relenza was launched in 1999, it promised to deliver what many people wanted - a cure for flu.

But doctors feared surgeries would be overrun with patients with mild symptoms, who believed they were in the early stages of flu wanting the �24-a-course drug.

Relenza comes in powder form. It can reduce the amount of time people suffer from flu to around two days, because it suppresses the replication of flu viruses, which then limits the typical flu symptoms of fatigue and fever.

But patients have to take the drug within 48 hours of developing the first symptoms.

And for it to work, the Mayday researchers said, "a significant amount" of the drug has to be inhaled into the patient's lungs.

It has already been established that the elderly can have problems using inhalers.

A statement from GlaxoSmithKline said studies had shown elderly people did find Relenza easy to use.

It said: "Recently published studies involving over 400 patients all aged 65 years or over, looked into patient experience of Relenza and reported there were no differences between the total patient population and the 'at-risk' (including elderly) in terms of perceived response to treatment and device handling."

The company added that the drug had also been shown to be as effective in patients over 50 as in the general population, reducing the duration of flu by 40%.

The research is published in the British Medical Journal.